This is a new application for a K02 Independent Scientist Award. The PI, Dr. Thomas Ernst, is the Director of Medical Physics at the Brookhaven National Laboratory (BNL). Dr. Ernst is an MR physicist with extensive experience in the development of neuroimaging techniques, and has been involved with the application of these exciting neuroimaiging techniques to neuropsychiatric disorders, particularly drug abuse and HIV, for over a decade. Dr. Ernst is PI on one NIH-funded research project (from NIMH), one large DOE-funded program project on biomedical engineering, and co-PI on two additional R01 grants (one from NIDA, and one from NINDS). The K02 award would allow Dr. Ernst to reduce his administrative duties, and re-focus his research on advancing MR techniques for translational research into drug abuse and HIV brain disease. Specifically, Dr. Ernst would spend 30% on methodological developments (10% directly on the MRI scanner), 20% on clinical projects, 10% on educational activities, and 15% on mentoring, for a total of 75% protected research time. The specific Methodological Aims of the proposed research are: 1. To introduce event-related fMRI designs to the study of drug abuse and HIV brain disease, and 2. to apply structural equation modeling (SEM) to the analysis of fMRI data in drug abusers and HIV-positive subjects. These technical advances will make it possible to address the following Clinical Aim: 3. To determine the effects of drug abuse and HIV infection, alone or in combination, on the connectivity of the working-memory network in the brain. The educational activities will be based on the strong collaborations with outstanding scientists and physicians at BNL and SUNY-SB, reading scientific literature, attending local seminars and scientific meetings, as well as participating in advanced educational courses at meetings. Another important part of Dr. Ernst's effort would be mentoring. Over the past decade, Dr. Ernst has mentored 18 young scientists. Eight of the past mentees now have faculty-positions, ten are working in drug abuse and HIV research, and six are currently supported or have applied for funding by NIDA.